Breast cancer primary prevention is a high research priority due to the high psychological and economic costs.The disease is a multistep process and several risk factors have been recognized. Over the past three decadesnumerous studies have investigated the association of lifestyle with breast cancer, showing independent effects ofvarious factors. We report here a summary of the present state of knowledge on the role of lifestyle patterns, suchas physical activity, diet, smoking, hormone therapy, and experience of psychological stress in the modulation ofbreast cancer in women, and discuss commonly accepted biological mechanisms hypothesized as responsible forthe associations. The findings indicate that regular physical activity of moderate to vigorous intensity is probablylinked with the decreased breast cancer risk among postmenopausal females and suggestive for a decrease of therisk in premenopausal women. In contrast, the consumption of high-fat diet, alcohol intake, and use of combinedestrogen and synthetic progestagen hormonal therapy may increase the risk. Epidemiological findings dealingwith a role of smoking and experience of psychological stress are conflicting.